Browsing by Author "Pueyo, JJ"
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- ItemChemical and hydrological evolution of the Mulhouse potash basin (France): are "marine" ancient evaporites always representative of synchronous seawater chemistry?(Elsevier, 2008-07-15) Cendón, DI; Ayora, C; Pueyo, JJ; Taberner, C; Blanc-Valleron, MMBrine reaction processes were the most important factors controlling the major-ion (Mg, Ca, Na, K, SO4, and Cl) evolution of brines in the Oligocene, Mulhouse basin (France) evaporite basin. The combined analysis of fluid inclusions in primary textures by Cryo-SEM-EDS with sulfate-delta S-34, delta O-18 and Sr-87/Sr-86 isotope ratios reveals hydrothermal inputs and recycling of Permian evaporites, particularly during advanced stages of evaporation in the Salt IV member. The lower part of the Salt IV evolved from an originally marine input. The basin was disconnected from direct marine inputs and a series of sub-basins formed in an active rift setting where tectonic variations influenced sub-basin interconnections and chemical signatures of input waters. Sulfate-delta S-34 shows Oligocene marine-like signatures at the base of the member. However, enriched sulfate-delta O-18 reveals the importance of synchronous re-oxidation processes. As evaporation progressed other non-marine and/or marine-modified inputs from neighbouring basins became more important. This is demonstrated by increases in K concentrations in brine inclusions and Br in halite, sulfate isotopes trends and Sr-87/Sr-86 ratios. The recycling of previously precipitated evaporites of Permian age was increasingly important with evaporation. This supports the connection of the Mulhouse basin to basins situated north of Mulhouse. The brine evolution eventually reached sylvite precipitation. The chemical signature of the resulting brines is not compatible with global seawater chemistry changes. The fast rate of intra and inter basin brine variations as well as the existence of contemporaneous brines with different chemical signatures, supports our interpretation. The existence of diverse non-marine inputs and associated internal chemical changes to the brine preclude the use of trapped-brine inclusions in reconstructing Oligocene seawater chemistry, without previously identifying all inputs. The general hydrological evolution of the Mulhouse basin is explained as a restricted sub-basin with a first marine stage. This gradually changed to a similar to 40% marine source at the beginning of evaporite precipitation, with the rest of inputs non-marine. The general proportion of solutes did not change greatly over evaporite precipitation. However, as the basin restriction increased the originally marine inputs changed to continental or marine-modified inputs from neighbouring basins north of Mulhouse basin. © 2008, Elsevier Ltd.
- ItemExploring the hydrochemical evolution of brines leading to sylvite precipitation in ancient evaporite basins.(Copernicus Publications, 2010-05-02) Cendón, DI; Pueyo, JJ; Ayora, C; García-Veigas, J; Blanc-Valleron, MMSylvite is a very common mineral in ancient evaporite deposits. Due to the absence of current deposits, the natural geochemical mechanism/s for synsedimentary sylvite precipitation and accumulation are not well understood. Numerous sylvite deposits or portions of them have been described as a result of diagenesis (i.e. Sergipe subbasin, Brasil). However, a number of deposits have been described as synsdimentary or being formed during primary evaporite deposition. It is the last group of deposits that can be studied to better understand the hydrochemical processes taking place in the brine at the onset of sylvite precipitation. The Salt IV sylvite beds from the Mulhouse potash basin, Alsace (France) have been described as synsedimentary in origin (LOWENSTEIN and SPENCER, 1990; CENDON et al., 2008). While sylvite in itself does not contain fluid inclusions viable for micro analysis, primary textures in neighboring halite are used as a proxy to understand brine evolution. Two halite-sylvite cycles from the B1 and B2 layers of the potash lower seam were selected. These exhibited clear primary halite crystal textures with sylvite adapting to an irregular halite sedimentary surface and finishing with a flat surface. The nine halite samples, selected at centimeter scale, provided close to 100 single fluid inclusion analyses, representing both the transition towards sylvite precipitation and the post sylvite precipitation. The fluid inclusion analyses revealed strong fluctuations in K concentration, well over the analytical error (<10%). These variations, in the same halite crystal, seem aligned in growth bands, with fluid inclusions within a certain growth band showing practically identical K concentrations, while neighboring bands exhibit a different concentration. Overall, the closer we are from a sylvite layer the higher K concentrations are. However, strong fluctuations continue when growth bands are compared. This pattern shows cycles of increasing K concentration along parallel growth bands with sharp falls followed by the initiation of a new increasing trend. The small “growth band” scale of the K concentration variations, suggests very sensitive processes within the brine with potential environmental changes (i.e. seasonal variations, day-night temperature fluctuations cycles) leading towards the final mass precipitation of a sylvite layer. © Author(s) 2010
- ItemFreshwater recharge into a shallow saline groundwater system, Cooper Creek floodplain, Queensland, Australia(Elsevier, 2010-10-15) Cendón, DI; Larsen, JR; Jones, BG; Nanson, GC; Rickleman, D; Hankin, SI; Pueyo, JJ; Maroulis, JFreshwater lenses have been identified as having penetrated the shallow regional saline groundwater beneath the Cooper Creek floodplain near Ballera (south-west Queensland). Piezometers were installed to evaluate the major-element chemistry along a floodplain transect from a major waterhole (Goonbabinna) to a smaller waterhole (Chookoo) associated with a sand dune complex. The floodplain consists of 2–7 m of impermeable mud underlain by unconsolidated fluvial sands with a saline watertable. Waterholes have in places scoured into the floodplain. The transect reveals that groundwater recharge takes place through the base of the waterholes at times of flood scour, but not through the floodplain mud. Total dissolved solids rise with distance from the waterhole and independently of the presence of sand dunes. Stable water isotopes (δ2H and δ18O) confirm that recharge is consistent with, and dependant on, monsoonal flooding events. Following floods, the waterholes self-seal and retain water for extended periods, with sulfate-δ34S and δ18O isotopes suggesting bacterial reduction processes within the hyporheic zone, and limited interaction between the surface water and groundwater during no-flow conditions. The area occupied by the freshwater lenses (TDS < 5000 mg/L) is locally asymmetrical with respect to the channel flow direction, extending down gradient along distances of 300 m. © 2010, Elsevier Ltd.
- ItemHalite fluid inclusion geochemistry of evaporite deposits in central Iran(International Union of Geodesy and Geophysics (IUGG), 2007-07) Shariatinia, Z; Cendón, DI; Pueyo, JJ; Rahimpour-Bonab, H; Hezarhani, AThe chemical analyses of major ions in primary halite fluid inclusions is widely used for the determination and characterization of brine chemistry and its evolution in ancient evaporite basins through the Phanerozoic (eg. Ayora et al., 2001; Brennan and Lowenstein, 2002; Horita et al., 2002; Kovalevich et al., 2002). The purpose of this study is to show the major ion compositional evolution and halite crystallization pathway in the Miocene, M1 member of the Upper Red Fm. (N, Great Kavir Basin, Iran). We show how the Rift setting of the Great Kavir Basin, exerted the main control on the modification of seawater major ion chemistry. Influx of Ca-Cl2 brines modified the earlier evaporated seawater into Ca- Mg- Na- Cl brines. In this case, the Ca2+ concentration of the evolving brine exceeded overall concentrations of SO42-, HCO3-, and CO32- ions, which is expressed as mCa2+>Σ(mSO42- + mHCO3- + mCO32-). From this modified brine MgSO4-poor potash salts (mainly halite, sylvite and carnallite) precipitated. The study of major ion variation for evaporite deposits in the mentioned area reveals that the evaporation path in the Great Kavir Basin was not the same as present-day seawater. The geochemical diagrams (e.g. Mg vs. SO4 and K) show that major ions followed different evolution trends. Seemingly, an externally Ca-Cl2 influx would have overridden the chemical signature of evaporated seawater within Great Kavir Basin. As a result, sylvite instead of K-Mg-sulfates precipitated, similar to that observed in other rift settings such as the Danakil Depression (Ethiopia) in Quaternary evaporates where secular seawater compositional changes can not justified the observed lithologies. Ayora C., Cendn D. I., Taberner C., and Pueyo J. J. (2001) Brine-mineral reactions in evaporite basins: Implications for the composition of ancient oceans. Geology 29(3), 251-254. Brennan S. T. and Lowenstein T. K. (2002) The major-ion composition of Silurian seawater. Geochimica et Cosmochimica Acta 66(15), 2683-2700. Horita J., Zimmermann H., and Holland H. D. (2002) Chemical evolution of seawater during the Phanerozoic: Impliations from the record of marine evaporites. Geochimica et Cosmochimica Acta 66(21), 3733-3756. Kovalevich V. M., Peryt T. M., Beer W., Geluk M., and Halas S. (2002) Geochemistry of Early Triassic seawater as indicated by study of Rt halite in the Netherlands, Germany and Poland. Chemical Geology 182, 549-563.
- ItemPalaeohydrology of the Mulhouse Basin: are fluid inclusions in halite tracers of past seawater composition?(Goldschmidt, 2007-08-19) Cendón, DI; Ayora, C; Pueyo, JJ; Taberner, C; Blanc-Valleron, MMBrine reactions processes were the most important factors controlling the major-ion evolution in the Oligocene, Mulhouse Basin (France) evaporite basin. The combined analysis of fluid inclusions in primary textures in halite by Cryo-SEM-EDS with sulfate-δ34S, δ18O and 87Sr/86Sr isotope ratios reveals hydrothermal inputs and recycling of Permian evaporites, particularly during advanced stages of evaporation in the Salt IV member which ended with sylvite formation. The lower part of the Salt IV evolved from an originally marine input. Sulfate-δ34S shows Oligocene marine-like signatures at the base of the member (Fig.1). However, enriched sulfate-δ18O reveals the importance of re-oxidation processes. As evaporation progressed other non-marine or marine-modified inputs from neighbouring basins became more important. This is demonstrated by an increase in K concentrations in brine inclusions, Br in halite and variations in sulfate isotopes trends and 87Sr/86Sr ratios. The recycling of previously precipitated evaporites was increasingly important with evaporation. Therefore, regardless of the apparent marine sequence (gypsum, halite, potassic salts), the existence of diverse inputs and the consequent chemical changes to the brine preclude the use of trapped brine inclusions in direct reconstruction of Oligocene seawater chemistry.
- ItemSulfate starved subbasins: implications for Permian seawater composition(Elsevier B. V., 2006-08-22) Cendón, DI; Pueyo, JJ; Ayora, C; Taberner, C; Peryt, TThe Zechstein evaporites represent a vast 1,000,000 km2 evaporitic basin of the Late Permian that extended from the British Isles to Poland and beneath the North Sea. The Zechstein evaporites of northern Poland precipitated in a subbasin of the Zechstein Sea forming the Peribaltic Gulf. Fluid inclusions in halites of the Polish Zechstein oldest Halite (Na1) have been analyzed by Cryo-SEM-EDS together with the δ34S δ18O of accompanying sulfates and Br contents in halite. The A1d (anhydrite) and Na1(halite and anhydrite) were chosen as they have the potential to better represent the original source of brine, minimizing common recycling processes within evaporitic basins. Fluid inclusions have major-ion compositions similar to evaporated modern seawater. Sulfate isotopes generally coincide with previous values for Permian evaporites assigned as marine in origin. However variations in both δ34S and δ18O are considerable when compared to smaller marine-continental settings such as the South Pyrenean basin (Ayora et al., 1994, Cendón et al., 2003). We postulate that the further restriction from the main Zechstein basin could have caused brines to be extremely sensitive to SO4-concentration variations, the result being that the Peribaltic Gulf could have been periodically starved of sulfate. This was registered by several isotopic reservoir effects during anhydrite and halite precipitation in the A1d and Na-1 cycles. Brines trapped in primary halite fluid inclusions in our data set are similar to those expected from the evaporation of modern seawater, except for SO4 always being depleted when compared to modern values. The palaeogeographic setting of the basin could explain why brines were depleted with respect to SO4, without the need to invoke more complicated global processes, such as secular variations in seawater chemistry. While these findings do not deny possible variation in seawater chemistry over the Phanerozoic, they reinforce the need for accurate interpretation of evaporitic precipitates. © 2006 Published by Elsevier Ltd.
- ItemZechstein saline brines in Poland, evidence of overturned anoxic ocean during the late Permian mass extinction event(Elsevier, 2011-11-24) García-Veigas, J; Cendón, DI; Pueyo, JJ; Peryt, TBromine concentrations in halite, sulfate isotopes (delta S-34 and delta O-18), and major ion concentrations in primary fluid inclusions from three boreholes in the Late Permian Zechstein evaporites have revealed sharp variations in marine derived brines within the Polish sector of the European Southern Permian Basin. The base of the Older Halite (Na2), during the latest Permian, registers a change from sulfate-rich brines, similar in composition to modern evaporated seawater, to sulfate-depleted brines (calcium-rich). This change coincides with a drop in delta S-34 to values close to +9 parts per thousand, not observed in delta O-18 counterparts. Opposite isotope (delta S-34-delta O-18) trends through the Na2 unit cannot be explained by changes in restriction conditions. We propose that the change to sulfate-depleted (calcium-rich) brines during halite deposition of the PZ2 (Stassfurt) cycle is related to the overturn of anoxic sulfidic deep-waters from the Panthalassa stratified superocean coinciding in time with the Permian-Triassic mass extinction event. The reconstruction of chemical changes in brines reveals two major evaporite sequences of increasing concentration that do not match the classic lithostratigraphic cycles. The first evaporite sequence (PZES-1) contain the evaporite units of the PZ1 (Werra) cycle, the PZ2 (Stassfurt) cycle, the Main Anhydrite (A3), and the base of the Younger Halite (Na3) of the PZ3 (Leine) cycle. The second evaporite sequence (PZES-2) is represented by almost the entire Na3 unit and the PZ4 (Aller) cycle. (C) 2011 Elsevier B.V.